<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			*{
				margin: 0;
				padding: 0;
			}
			.bigbox{
				position: relative;
				width: 100%;
				height: 500px;
				background-color: azure;
			}
			.bigbox .lftbox{
				position: absolute;
				top: 50%;
				left: -50px;
				transform: translateY(-50%);
				width: 50px;
				height: 50px;
				background-color: #87cefa;
				transition: all .5s linear;
			}
			.bigbox:hover .lftbox{
				position: absolute;
				top: 50%;
				left: 0;
				transform: translateY(-50%);
			}
		</style>
	</head>
	<body>
		<div class="bigbox">
			<div class="lftbox"></div>
			<div class="rightbox"></div>
		</div>
	</body>
</html>